Database for CTM model validation studies

NOXAR (May 1995-May 1996, Aug-Nov 1997)

In the Swiss NOXAR project a fully automated measurement system was permanently installed on a Swissair B-747 passenger aircraft during two extended time periods. Measurements of ozone, NO and NO2 were performed on roughly 700 individual flights between Europe and the United States and between Europe and the Far East (Bombay, Hong Kong, Beijing). Measurements were recorded at 3-sec time intervals and stored together with a number of meteorological and flight parameters.

The overall objectives were to create the first representative data set of NOx observations in the upper troposphere/lower stratosphere region of the Northern Hemisphere including a complete annual cycle, and to estimate the contributions from aircraft emissions and other NOx sources.

Special remarks concerning ETHmeg database content

Since the airliner was always flying in air traffic corridors the measured NOx value are somewhat biased by recent aircraft emissions. By subtracting the frequently observed short NO peaks associated with the crossing of aircraft exhaust plumes mean NOx concentrations in mid-latitudes are reduced by roughly 20%. Such aircraft plume peaks were excluded from the 1995/1996 dataset but not from the 1997 data. 22 (out of 38000) points with NO concentrations of less than -80 pptv were eliminated from the dataset. Most of these points were measured during late June/early July when the standard instrument was replaced by an identical device (but obviously with reduced performance) during about 1 week.